1. Field of the Invention
The present invention relates to an improved rotary drilling tool having great efficiency in cleaning the cutting face.
2. Description of the Prior Art
Rotary drilling tools are already known comprising a body having a first end connected to rotary drive means and a second end defining the cutting face. Such tools are described in the U.S. Pat. Nos. 3,645,346; 4,323,130; and 3,838,742 and the British patent GB-A-2 047 308.
It is also known to improve cleaning of the cutting face and removal of the spoil or cuttings by positioning nozzles whose jets are slanted with respect to the cutting face and therefore strike the wall at an incident angle different from 90.degree..
A drawback of the prior art resides in the fact that the distribution at present adopted for these jets does not promote good cleaning of the central part of the tool, which limits the feeding speed performances of the tool and increases the wear thereof.
The object of the invention is to propose an improvement to drilling tools so as to increase the performances thereof by more efficient removal of the spoil or cuttings from the cutting face and more particularly in the central part, or central zone, of the tool.
The present invention may be applied to drilling tools or drilling bits working by removing chips (blade tools) or by abrasion. The first tools mentioned generally comprise cutting elements made from polycrystalline synthetic diamond, the second generally comprises natural diamonds.